Gun sight



uly w46 JQDTEAR ET AL 'GUN SIGHT Filed March. 20, 1941 9 Sheets-Sheet l July 30, i946. J. D. TEA-R ETAL $0,068

GUN SIGHT Filed March 20, 1941 9 SheetS-Sheekl 2 ATTORNEY juh @y w45@ J. D. TEAR ET AJ..l 2495?@@8 GUN SIGHT Filed March 20, 1941 9 Sheets-Sheet 3 j l INVENTORS JAM as imam f .ELLQYT P. Ross ATTORNEY J. D. TEAR ET AL f3-@68 GUN SIGHT Filed March 20, 1941 9 Sheets-Sheet 4 INVENTORS JAM D'AR s ELU@ mmss July 30, 15946.

J. D. TEAR ET AL GUN SIGHT Filed March 20, 1941 9 Sheets-Sheet 5 INVENTORS JAMES DJEAR ELLIOTT R R055 Y,luraroznvEY Fully 3, i946. J. D. TEAR ET AL GUN SIGHT Filed March 20, 1941 9 Sheets-Sheet 6 R 5 5 Ems my OTO EA maa. m. @www WMM AU JL E Juy 3, 1946. D. TEAR ETAL GUN SIGHT Filed March 20, 1941 9 Sheets-Sheet '7 ELUOTT P` ROSS ATTORNEY July 30, 1946.

J. D. TEAR'ET AL QUN SIGHT Filed March 20, 1941 9 shelet/-sheet 8 I INVENTORS JAMES D TEAR ELLIOTT P. ROSS ATTORNEY GUN SIGHT.

Filed March 20, 1941 9 Sheets-Sheet 9 INVENTRS JAMES DTEAR BY ELLOTT P. ROSS ATTORNEY Patented July 30, 1946 GUN SIGHT James D. Tear, Great Neck, andElliott P. Ross, Forest Hills, N. Y., assignors to Ford Instrument Company, Inc., Long Island City, N. Y., a corporation of New York Application March zo, 1941, serial No. 384,236

(o1. sas-49) i claims.

This invention relates to gun sights which are automatically displaceable relative to the gun in accordance with the rate of movement/ of the gun, and particularly to sights for guns that are mounted in fixed positions on a firing ship such as, for example, an airplane.

The directing of a gun iixedly mounted 0in an airplane has been a diiiicult problem because the gun has to be trained and elevated with reference to a target by adjusting'the horizontal and azimuth position of the airplaneand it Was nec.

essary for the pilot to approximate the angle that the airplane had to lead or point ahead of and above the target that the projectile would intercept the target. 1

The problem is further complicated because consideration has to be given to the changes in the rate of change of bearing of the target as a firing airplane closes in from one side on a Inoving airplane target.

The solution of the problem also involves the application of elevational movement of the sight vrelative to the gun to compensate for the rate of change in the vertical plane of space of the position of the firing airplane relative to the target and forthe shape of the trajectory of the pro'jeotile, which is a function of the range.

The object of this invention is to provide an apparatus to position the sight relative to the bore of a gun, that is flxedly mounted in the horizontal plane of and parallel'to the longitudinal horizontal axis of a ring airplane, in accordance With the instantaneous Vrates of change of bearing and elevation respectively of the target and the range of the target.

For the purpose of this speciiication and the appended claims the longitudinal horizontal axis of the ring airplane and the longitudinal horizontal axis of the casing supporting and housing the mechanisms are defined as the center line of the airplane and the center line of the casing respectively.

The particular mechanisms disclosed herein as` embodiments of the invention are illustrative of mechanisms used to apply the invention to the problem of directing a gun nxedly mounted on one airplane ring on another airplane as a target, but it will be understood that the invention has other applications, such as directing a gun on any form of mount Where the sight for directing the gun is displaced fromthe bore of the gun an amount depending uponfthe 'rate of` vangular movement of the gun `or gun mount. g

The mechanisms include an inertia element that inherently resists any change in its position in Space, such as a gyroscope. The gyro is mounted on supporting arms and concentric rings and is free to rotate about its horizontal an'd its vertical mounting axes. fThe arms are mounted in a director casing or frame `Whiohisv Vix pivoted to rotate about horizontal and vertical axes.

Two motors are mounted in the' casing and connected through follow-up controls to maintain the centerline of the casing parallel to the spin axis of the gyro and at the same time to apply precessing forces to the gyro to cause the gyro to prec'ess toward the centerline of the airplane at a rate directly proportional to the displacement of the centerline of the casing from the centerline of the airplane. The gyro is mounted in the casing with its spin axis parallel to the centerline of the casing when the gyro is in its mid or neutral position. A conventional sight is xedly mounted in such a position on the casing that its optical axis is parallel to the centerline of the casing. It will thus be seen that when the casing is in its neutral position relative to the airplane or gun and the gyro is in its neutral position relative to the casing, then the centerline of the airplane, the optical axis of the sight, the centerline of the casing, and the spin axis of the gyro are all parallel to each other,

When such a gyro and casing with its associated sight are mounted in an airplane that is maneuvered to keep the sight pointed at another airplane or any other object as a target, any tendency for the airplane to change its position relative to the gyro is used to automatically determine the instantaneous rate of change of direction of the line of sight in the horizontal and vertical planes of space.

It is Well known in the fire control art that the horizontal displacement of the sight from the bore of the gun (deflection or Ds) is directly proportional to the rate of change of bearing (dB) and the time of flight (t) of the projectile and that the time of flight of the projectile is a function of the range (R). This relation is expressed by the equation From this equation itis seen that the rate of change of bearing is directly proportional to the deiiection (Ds) and inversely proportional to the time of flight (t) or range (R). It is therefore to be understood throughout the specification and claims that'the Word range is intended to include a function of range or time of flight.`

The motor, in the casing, which is connected to move the casing in azimuth to keep its centerline parallel to the spin axis of the gyro, applies the corresponding precessing force to the gyro through a dividing mechanism to cause the gyro to precess in azimuth at the rate dB, which, as shown by Equation 1 is directly proportional to the deiiection (Ds) and inversely proportional to the range (R). The effect of this combination is to offset* the centerline of the casing and thereeficaces e fore of the sight from the bore ofthe gun by the deection (Ds) .and to apply a precessing force to the gyro equal to the rate of change of bearing of the target, when the range (R) is set into f,

'the dividing mechanism. This precessing force acting on the gyro will cause the gyro to precess at the same rate the firing airplane must changeVV heading or the gun must be trained or elevated, to keep the sight pointed at the target, while theY sight is offset from the gun the proper amount to allow for the movement of the target during the time of flight. Y

The motion of the firing airplane through Yspace (dE)` and the time of flight (t) of the projectile,

which is a function of the range (R). VThis relation is expressed by the equation Es v `Es=olE R or dE R- (2) `Thesecond motor is therefore connected to apply a 'precessing force to the gyro directly proportional to the vertical Vdisplacement of the sight from the gun and inversely proportional to th-range and tormove the casing in Aelevation toY keep its centerline horizontally yparallel to theV spin aXis of the gyro. *A

Modifications of the invention are disclosed in oneof which changes in rates, as indicated yby movement of the follow-up motors', are utilized to displace the follow-up controls to cause the sight tobe momentarily delayed inv attaining its new posi-tion relative to the gun. The eiect oi this delay is that the operator senses any change in the rate of turning of the airplane or gun mount immediately upon changing the control.

A second modification discloses a connectionv from Vthe motors to the gyro to cause the gyro to be precessed by movement of the motors. in addition to thevprecessional rate applied tothe gyro because of the rotary position of the motors or' the sight relative to the gun. The effect of this second precessing force is to cause the gyro and the sight to be moved toward the target in addition to the movement due to the continuously applied precessing force.

The details of apparatus to accomplish the desired functions will now be described in detail.

In the drawings:

Fig. 1 is a plan view showing the positional re-l lation of one airplane iring on another-airplane as a target, as the firing airplane is closing in on the. targetirom one side;

Fig. -2 is a horizontal cross-sectional view of the casing showing the mechanisms ofthe invention, taken on line 2- 2 of Fig. 3;

Fig. 3 is a vertical cross-sectional View ofthe casingand mechanisms, Vin the simplest form, taken onthe centerline 3 3 of Fig. 2, except-that the gyroand the associated precessing arms are shown in elevation;

' Figjl is a vertical cross-sectional View of Ythe casing and mechanisms taken on line 4'-4 of F153; 1 v

Fig. 5 View similar to Fig. 4 taken online 5-1-5 of 3; 1 j

Fig. 6 is a View .similar to Fig. 3 butfshowing the added parts of one modification;

Fig. 'l is a vertical cross-sectional View of the casing and mechanisms ,taken online 1-'I of Fig. 6;

Fig. 8 is a view similar to Fig. 3 but showing fthe added parts of a second modification;

Fig. 9 is a vertical cross-sectional view of the casing and mechanisms taken on line 9-9 of Fig. 8, and I Fig. 10 is a wiring diagram showing ther electrical connections.

AWith reference to Fig. 1, I represents an air- I 1 plane having a gun 2 xedly mounted parallel 1 to theecenterline of the airplane. The line 3 rep'- Y being re'd at another airplane ortarget 4. TheY resents the direction of the line of sight relative to the centerline of the airplane I, as the gunis line v5 represents the direction of the path of the firing airplane I and the direction of the path of the projectileV to the intercept point 2a. The angle between the'lines 3 and 5 is the deflection angle (Ds). l

Referring'to Figs. 2 to 5, inclusive, and particularly to Fig. 3, 6 represents a'casing mounted for rotation about its transverse horizontal axis on ball bearings '1,1 one of which is supported byV trunnion Ta, upright brace 8 and frame 9, and

the other of which is supported vby frame Vl). Frame 9 is mounted to rotate about itsjvertical axis in ball bearings I0 supported vin base II. Base Il is mounted on some suitable support of the airplane with the lower face of base II in the horizontalt plane of the airplane.

Access to the inside of the casing is had through openings I2 in the front and back Walls of the casing 6. The openings I2 are covered by plates I3 secured to the casing 6 by bolts. A cover plate I3a is secured to frame 9 to protect the gearing mounted on the frame 9. y

To the' inside walls of casing B are secured two cross-straps I4 and I5 which act as supports for pivots I6 on which ring II is mounted. Onthe walls of casing 6 are also secured two arms I8 and I9, which act as supports for pivots 20 and 2| on which ring 22 is mounted. Pivotally mounted in'ring 22'is gyro .23. e

The casing of the gyro 23 carries pins `24 which extend along the s pin axis of the gyro andengage slots 25in ring I1. whereby a rotational force is applied to ring I'I about its vertical axisto apply a force to gyro 23 to precessit about its horizontal axis on pivots 20 and 2 I`. The rotational force is applied to ring II aboutits vertical axis by arm 26 which is rigidly connected to ring I'I. The mechanisms to applythe force to arm ,26 will be described hereinafter. I Y Y.

Also secured to ring Il is arn 1.21 on the end of which is mounted a roller 28which ,engages electrical contacts 29 which are insulated from each other andv from a frame 30 to which they are secured. Frame 30 is held in position by bolting it to strap I5. The contacts 29 and roller 28 serve to control the deection motor 3I the function of which will be described hereinafter. roller 28 is connected to a power supply by the i conductor 28'. 'Ihe contacts 29 are connected to 33 on the end of which is mounted roller 34 which is connecteclto thepower supply by aconductr 34. Roller 34 cooperates with contacts 35 which Y The are insulated from each other and from an arm 36 on which they are supported. Roller 34 andv contacts 35 serve to control elevation motor 31. The contacts 35 are connected to motor 31 through conductors 35 and motor 31 is connected to the power supply by conductor 31. Arm 36 depends from arm |8.

Deflection motor 3| is connected by gears 38, 39, 48, 4|, shaft 42, gears 43, shaft 44, gears 45, 43 and 41, to a circular, toothed plate 48 secured by bolts to base It will thus be seen thatmotor 3| `will drive the frame 9 and the supported mechanism in azimuth, that is, about its vertical axis.

Elevation motor 31 is connected by gears 49 and 50, shaft 5|, and gear 52, to a toothed arcu- V ate arm 53 extending downwardly fromtrunnion 1a which is secured against rotation in brace 8 by key 54. It will thus be seen that motor 31 will drive casing 5 about itstransverse horizontal axls.

' Referring particularly to Figs. 3 and 5, gear 4| previously described is also in mesh with rack teeth on slide 55 which is one input of a conventional divider 56. Slide 55 is supported in a grooved guide 55a secured to the walls of casing 6. The other input slide 51 of divider 56 ismoved by gear 58 on shaft 59 which is set in accordance with the range of the target by either of the knobs B9. Dials 3| on shaft 59 cooperate with indices 62 to indicate the set-in value of the range. y v

The output link E3 of divider 59 is located by the intersection of slides 55 and 51 in its central portion and is pivoted at its lower end on pin 64 which is secured by bolts tothe arm I9. The out@i f put or upper end of link 63 is pivotally connected to slide 65 which moves in guide 55 secured to the walls of casing 6.

At the ends of slide 65 are mounted pins S1 and 88 which support spring 69. The center point of the spring 69 is connected to the upper end of arm 32 previously described. Y

The motion of motor 31 transmitted to shaft 5| is also transmitted to gear 19 which is pinned to shaft 5|, and thence through gears 1| and 12to slide 13, which is one input of a conventional divider 14. The other input to divider 14 is slide 15 which is set in accordance with the range Aby gear 15 connected to shaft 59 which is moved as previously described. The output link 11 of divider 14 is located by the intersection of slides 13 and 15 and is pivoted at its lower end on pin 18 secured to arm I8. The output end of link 11 is pivoted to slide 19 which moves in guide 8i) secured to the walls of casing 3.

At the center of slide 19 is mounted pin 8| which is connected to the center of spring 82 the ends of which are connected to wire 83. Wire 83 passes over grooved pulleys 84 mounted on the top wall of casing 3. The center of wire 83 is connected to arm 26 previously described.

A conventional sight 85 is mounted on the top of casing 6 with its optical axis parallel to the centerline of the casing.

Operation (deflection) If the ring plane l is flying straight ahead, the gyro, casing and sight will be automatically brought to their mid position parallel to the gun bore by the action of the motors 3| and 31 under the control of contacts 28-29 and 34-35 respectively. For example, if the gyro and casing are to the left of the mid position, a precessing force will be applied tothe gyro to cause it to precess to the 'right ata reducingrate -until the gyro 6. comes to the mid position when the rate'will be zero and the sight will be parallel to the bore of the gun and the centerlineof the airplane.v Now, if the airplane is turning, say to the right, to follow and close in on a target in a relative position as indicated inFig. 1, the spin axis of the gyro will tend to'keep its position-in space and there will be a relative counter-clockwise movement of the spin axis-of the gyro from the centerline of the casing and the centerline of the plane. As a result of this relative movement roller 28 comes in physical contact with one ofthe electrioalcontacts 29 and motor l3| turns the casing E counterclockwise about the base through gears 39, 48, 4|, shaft 42, gears 43, shaft 44, gears 45, 45 and 41, until the casing is moved to bring the centerline of the casing parallel to the spin axis of the gyro. At the same time the motor 3| applies a precessing force on the gyro 23,v through gear 4|, slide 55, divider 56, spring 69, and arm 32, proportional to the displacement of the sight from -thebore of the gun divided by the range, until the clockwise-rotational rate of the spin axis of the gyro is the same as the true clockwise movement of the airplane, when a balance is obtained and the proper deection is set up in accordance -withthe equaltion Ds=dBR. i

The generation of the rate of change in elevau tion and the setting in of the correction in elevation isaccomplished in thesame manner `as that for the rate of change ofsbearing and the deiiection correction previously described.

The modification of theinvention shown in Figs. 6 and 7 differs Vfrom. thateshownV in Figs. 3` to 5 inclusive only inthe action of the controls for the deflection and elevationrmotors, 3| and 31 respectively. Since the same numbers are? used for correspondingfparts their operation` or vconstruction Will not be described except as the Vadded partsof the modification aiect their operation.

rThe difference in the controls is that the frame 30 and the arm 36, carrying the Acontacts 29 and 35 -respectively,instead of being rigidlyrsecird to cross strap |5 and arm |8 are yieldably mounted relative thereto andare displaceable from their normal central position in accordance with the speed and direction of rotations of the motors 3| and 31 by means of drag devices 83 and81 respectively.

The drag device 83 consists of a shaft 88 carrying a disk 89 integral therewith. The frame 38 is secured to a hub 90 which is pinned to the shaft 88 and carries'an arm 9| the-outerend of which is normally centered by two springs 92 connected to eyes 93 in the side of casing E. The upper end of shaft 88 is rotatably mounted in the cross strap I5 on the same axis as the pivot|5 and the lower end is mounted in cross strap 94.

The disk 89 is enclosed in a housing 95 which carries a gear 96 meshing with a gear 91 mounted to be rotated by deiiection motor 3| through gears 38 and 39. The housing 95 is lled with oil or other liquid so that rotation of the housing by the motor causes a drag on the disk 89 which displaces the frame 39 and contacts 29 from their normal central position at which they are held by springs 92. This displacement is proportional to the speed of rotation of the motor 3|.

Thedrag device 81 is similar to drag device 86 and consists of a Shaft 98 -having an integral disk Y99 enclosed in a housing |00, one side of which is gear 12 driven by elevation mot-or 31 through gears 49, 50, 19 and 1|. 4The shaft 98 is mounted at one end in casing 6 and at the other end in arm' |8 on` the"same axisV as pivot 20. yThe arm 36 is secured to a hub, |0|A which is pinned to shaft 98 andcarries a' second arm |02 thevouter end ofwhich is connected to springs |03 which are connected to eyes |04 mounted,v on the wallsof casing 6. The housing vis filled with oil or other liquid s0. that rotation of the elevation motor 3l, displaces the arm 36 and contacts 35 from their normallylcentral position an amount `proportional to the speed ofthe motor.

The Vdisplacement.ofthe contacts 29 and 35 loy from their normal position relative to the lcasing Y due to the drag devices is in the direction 'the casing is moved bythe motors 3| and 31 :respectively, and an amount proportional to the speed of the motors. v 1 Y The effect of vthis displacement on the operation irs-,that When the operator changes therate of change of course of the firing airplane to bring thesight on the target, thel sight instead of being maintained continuously parallel to the spin axis of the gyro by the follow-up motors is displaced therefrom in the direction the operator is changing the rate of turning of the firing airplane and the operator therefore will see a temporary move-Y ment of theV sight relative to the `target in the same direction he is changing the, rate ofturning. Because vof this movement the tendency of the operatorto overcorrect the changeyof heading'is.reduced. :V I .y 1, v f 1 The modication; of atheY inventionv shown; in Figs..8 and 9 dlifersirom that; shown-in Figs. 2 to 5, inclusive, by the additionof a second precessing connection from each .of the ,motors 3| andLBl to the' gyro 23.; `In addition'to .the connections throughvthe dividers-56 and '|4by1which the' gyro is Vcaused to precess all-.a rate proportional to the displacement of the casing andv sight from the vbore ofthegun, a second connection is provided from each motorrincluding a drag device Which applies va'precessing force to the gyro in proportion to thez-rateof turningof the motor, which rate corresponds to the rate of movement of the casingjand sight relativeto the gun. The drag device lisgactuated byfthedelection movtor 3| to apply `forces tothegyro tocause precession in train and-gthe drag v device |06 is actuated by the elevation motor3| to apply1forcesfto the gyro'to cause precession' in elevation.v ,1

The drag device |05 consists of a dragfdskl'l secured on shaft 42 which is rotatedby deflection motor 3I.Y A housing |08, enclosing disk |01, is free to rotate on shaft 42V andis lled with oil or other` liquid. The housing |08 has a bossV |09 on one' side (see 1=ig.;v 9) carryingapin |'|V0-to which is connected-one end of a link the other end of which is connected to a pin ||2 o an arm ||3 extending vfromring22,

The drag -device |06 consists of a a .dragV disk ||4 integral with shaft I5 which passes through Y the cross strap |5 and isA secured in ring |1, thereby forming the lower pivot forring Il. The disk H4 is enclosed in a housing ||6which rotates on shaft ||5l and is filled'with oil or other liquidi.V 'Ihe housing H6 carries a gear Il meshging; with a gear ||8 on shaft 5| which is driven byelevation motor3l. u f .Y

V`rI'he effect of the drag devices ofy this modificationvon-the operation ofthe sightis to cause the gyron and sight tobe moved in space in the vdirection of the changev of rate as determined by the follow-up contact-.sand the motors.A Forexample if the Pilot is. following a targetfsothat the 'firing plane isturnjma to the` right andV tht pilot notices that the line'of Asight is falling loehind the target, he will turn his airplane Vfaster to the rightwhich will cause the motor 3l to start to move the sight to the left relative to the gun and to increase the rate of training of the gyro to make its rate the same as the relative angular movement of the target. This change of rate of itself will not cause the sightto catch up with the target but the action of the drag device |05 will apply va second processing force to theA gyro due to the rtation of the motor3| which force will cause the gyro to precess momentarily in the direction of the target. VThis precessing of the gyro is in addition to that applied through the divider 56. y

It will be seen that Whenever the sight moves off of the target the change of the rate of turning orflthe airplane made by the pilot will not only change the rate of continuous precessing of the gyro but will momentarily cause the gyro Vto precess additionally in a direction to bring the line of sightv back on the target. Y

Similarlyv any movement of the sight from the target in elevation will be corrected both in rate and position by the pilot changing the rate of turning of the airplane in elevation.

While theinvention has been described as applied to a sight for a gun-xedly mounted on an airplane, so that theyrate of turningof. the airplane to keep the vsight on'the target automatically displaces the sight from the gun the proper amount to allow for movement of the target.v during the time of flight, Vit is obvious that if the sight mechanism is secured to the gun cradle of any gun mount the movement of the mount to keep the sight on the target will automatically offsetl the sight the correct amount fromv the bore of theY gun. Likewise the sight mechanism if mounted on a dummy gun cradle may be usedas. a director and the position of the dummy gun transmitted to the real gun may be used Vto position the real gun.

Itis obvious that various changes Amay be made by those skilled in the art in the details of the invention as disclosed in the drawings and described above Within the principle and scope of the invention as expressed in the appended claims..

We claim v 1. In .combination with a manipulatable device, sighting means comprising a casing -pivoted on the device for relative angular movement about a predetermined axis, a sight carried by the casing, a'gyroscope universally mounted in the casing, a motor mounted onV the casing and controlled by relative angular movement between the casing and the gyroscope about the predetermined axis, a connection between the motor and the device vto impart angular movement to the casing relative to the device, means actuated' by the motor for developing a force proportional to the angular rotation of the motor, and means for applying the force so developed as a precessional force to the gyroscope. Y Y

2. Directing means comprising almanipulatable support, a sight mounted on said support for universal pivotal movement, a gyroscope universally mounted on said support,A an energy storing device operable to applya precessional force to the gyroscope, a motor controlledY by relative angular movement betweenv the sight and the gyroscope and rotative in proportion to -thegangular displacement between the gyroscope and the sup-- port, means operated by the motor to impart energy into the energyvstoring device proportional to the rotative position of the motor, and operative means between the motor and sight to adjust the angular position of the sight relative to the support proportional to the rate of angular movement of the support.

3. Directing means comprising a manipulatable support, a sight mounted on said support for un'.- versal pivotal movement, a gyroscope universally mounted on said support, an energy storing device operable to apply a precessional force to `the gyroscope, a motor controlled by relative angular movement between the sight and the gyroscope and rotative in proportion to the angular displacement between the gyroscope and the support, means operated by the motor to impart energy into the energy storing device proportional to the rotative position of the motor, operative means between the motor and sight to adjust the angular position of the sight relative to the support proportional to the rate of angular movement of the support, and means for modifying the proportion between the rotative position of the motor and the energy imparted to the energy storing device by the motor.-

4. A sight mechanism for a gun xedly mounted on an airplane, comprising a` casing mounted on the airplane for angular adjustment about two axes, a sight carried by the casing, a gyroscope in the casing mounted for freedom of movement about two axes substantially parallel to those of the casing, two motors connected to adjust the angular position of the casing about the respective axes, control means for the motors operative in response to relative angular movement between the casing and the gyroscope about the respective axes, means actuated by each motor for developing a force proportional to the angular adjustments of the casing relative to the gun about the respective axes, and means Vfor applying the forces so developed as precessional forces to the gyroscope to cause precession of the gyroscope about the respective axes. v

5. A sight mechanism for a gun xedly mounted on an airplane, comprising a casing mounted on the airplane for angular adjustment about two axes, a sight carried by the casing, a gyroscope in the casing mounted for freedom of movement about two axes substantially parallel to those of the casing, two motors connected to adjust the angular position of the ycasing about` the respective axes, control means for the motors operative in response to relative angular movement between the casing and the gyroscope about the respective axes, means actuated by each motor for developing a force proportional to the angular adjustment of the casing relative to the gun about the respective axes, means for applying the forces so developed as precessional forces to the gyroscope to cause precession of the gyroscope about the respective axes, and means for modifying the proportion between the adjustment of the casing and the forces developed.

6. A sight mechanism for a gun rlxedly mounted on an airplane ring at a target, comprising a ibase mounted on the airplane with its vertical axis parallel to the vertical axis of the airplane, a frame mounted on the base for rotary movement about a vertical axis parallel to the vertical axis of the base, a casing pivotally mounted on the frame for rotation about a transverse horizontal axis, a sight mounted on the casing with its optical axis parallel to a centerline of the casing, a gyroscope universally mounted in the casing with its spin axis and its vertical mounting axis parallel respectively to the centerline of the casing and the vertical axis of the frame when the gyroscope is in its neutral position relative to the casing, power means mounted in the casing, means actuated by relative angular movement between the gyroscope and the-casing for controlling the power means, means connecting the power means to the base for rotating the Yframe and `the casing about the vertical axis,

and means connecting the power means to the ,gyroscope-for applying forces to the gyroscope to precess it about its vertical axis at a rate proportional to the rate o-fangular movement of theairplane about its vertical axis including means settable in accordance with the range of the target.

'7. A sight mechanism for a gun xedly mountned on an airplane firing at a target, comprising a basemounted on the airplane with its vertical axis parallel to the vertical axis of the airplane, a frame mounted on the base for rotary movement about a vertical axis parallel to the vertical axis of the base, a casing pivotally mounted on the frame for rotation about a transverse horizontal axis, a sight mounted on the casing with its optical axis parallel to a centerline of the casing, a gyroscope universally mounted -in the casing with its spin axis and its vertical mounting axis parallel respectively to the centerline of the casing and the vertical axis of the frame when the gyroscope is in its neutral position relative to the casing, power means mounted in the casing, means actuated byrelative angular movement between the gvroscope and the casing for controlling the power means, means connecting the power means to the frame for rotating the casing about its transverse horizontal axis, and means connecting the power means to the gyroscope for: applying forces to the gyroscope to precess it about its horizontal axis at a rate proportional to the` rate of angular movement of the airplane about its horizontal transverse axis including means settable in accordance with the range of the target..

8. A sight mechanism for a gun xedly mounted on an `airplane firing at a target, comprising a base mounted on the airplane with its vertical axis parallel to the vertical axis of the airplane, a frame mounted on the base for rotary movement about a vertical axis parallel to the vertical axis .of the base, a casing pivotally mounted on the frame for rotation about a transverse horizontal axis, a sight mounted on the casing with its optical axis parallel to a centerline of the casing, a gyro universally mounted in the casing with its spin axis and its vertical mounting axis parallel respectively to the centerline of the casing and the vertical axis of the frame when the gyro is in its neutral position relative to the casing, power means mounted in the caning, means actuated by relative angular movement between the gyro and the casing for controlling the rotation of the power means in accordance with the angular position of the spin axis of the gyro relative to the gun, transmission means connecting the power means to the base and to the frame for rotating the frame and the casing about their vertical and transverse horizontal axes respectively, and transmission means connecting the power means to the gyro to apply forces to the gyro to cause precessio-n about its vertical and its horizontal axes at rates proportional to the rates of angular movement of the airplane about its vertical and horizontal transverse axes, respectively, the connecting means includinggmeans settable in accordance with the'range of the target. V l

9; A sight mechanism for a gun xedly mounted on an airplane firing at a target, comprising a base mounted on the airplane with its vertical axis parallel to the vertical axis of the airplane, a framey mounted on the base for rotary movement about a vertical axis parallel to the vertical axis of the base, a casing pivotally mounted on the frame for rotation'about a' transverse horizontal axis, a sight mounted on the casing with itsf optical axis parallel to a centerline ofthe casing`,`a gyro universally mounted in thecasing with its spinaxis and its vertical mounting axis parallel respectively to the centerline of the casing and the vertical axis of the frame when thev gyro is in its neutral position relative to the casing, train and elevation power means mounted in the casing, means actuated by relative angular movement between the gyro and the casing for controlling the rotation of the power means in accordance with the angular position of the spin axis of the gyro relative to the gun, anpair of mechanical dividingmeans settableY in accordance with the range of the target, means fori connecting the Vrespectivepower means-to the respective divldingmeans, and means for connecting the outputY of thev respective dividing means vto the gyro for applying forces" to the gyro,Y whereby the gyro is precessedabout'its vertical axis and its horizontal axis at rates 'proportional to the angularposition of the spin axis of the gyro relative' to the gun and inversely proportional to thefrange of'th'cta'rget; Y

10. 1n combination 'with an angularly movable gungsighting means comprising av casing pivoted for angular adjustment relative tothe gun,`a sight carriedV by Ythe casing, a gyroscope; universally monntd in the casing, a motor connected to adjust the angular position of thecasing relative to the gun, means actuated'by the motor for developing a force 'proportional to the angular adjustment of the casing relative to the gun,v means for applyingthe-force so developed to the gyroscope as aprecess' ing force, and'control meansV for the Y motcirY actuated'n'byangular *movement of the gyroscope relative to the casing', said control meansV including` 'a part displaceable in accordance with the speed of the motorandoperable to delay the action of the motorfin adjusting theangular position'of the casing relative tothe gun. Y

11. A sighting mechanism for. an angularly movable gun, comprising a casing mounted for angular adjustment relative to the gun about two mutually normal axes, a sightv carried by the casing, a gyroscope mounted in the casing for angular movement about two axes normallyparallel to those ofthe casing, two motorsy connected to adjust the angular position of the casing relative to the gun about the respective axes, meansactuated by the respective motors for developing forces proportional to the angular adjustment of Ving a part displaceable by and in accordance with the speed lof the controlled motor and operating to'delay the actionof the motor in adjusting the angular position of the casing relative 'to the gun about the respective axes.

respective axes.

12 f 12. A sighting mechanism for an angularly movable gun, comprising a sight mounted for angular adjustment relativeto the gun about two mutually normal axes, a gyroscope mounted for angular movement about two axes normally parallel to those of the sight, two motors connected to adjust the angular position of the sight relative to the gun about the respective axes, means actuated by the respective motors for develfoping forces proportional to the angular adjust- 13. A sighting mechanism for an angularly 'movable gun, comprising a sight mounted for angular displacement relative to the gun, a gyroscope mounted for angular displacement relative to the gun, power means operable in response to diierences in the angular Idisplacements of the sight and the gyroscope relative to the gun to adjust the angular displacement of the sight rela tive to the gun, means actuated by the motor for developing a force proportional to the angular displacement of the sight from the gun, and means for applying the force to the gyroscope to cause precession of thel gyroscope inthe direction of movement of the gun and at a rate proportional to the Vforce'. g

V14. A sightingfmechanism for an angularly movable gun, comprising a sight mounted for angular displacement relative tothe gun, power means operable to angularly displace the sight relative to the gun, a gyroscope mounted forv angular displacement relative to the gun,'means actuated by the power means for developing ya force proportional to the angular displacement of the sight from the gun, means for applying the force to the gyroscope to cause precession of the gyro- Vscope in the direction of movement of the gun at a rate proportional to the force', and control means for said power means actuated byrelative ydisplacement between the sight and the gyrothe power means.

15. A sighting mechanism for an angularly movable gun, comprising a sight mounted "for angular displacement relative to the gun, a gyroscope mounted for angular displacement relative to the gun, power means operable to maintain the sight parallel to the spin axis of the gyroscope, means actuated by the power means for developing a force proportional to the angular displacement of the sight and the gyroscope from the gun,

lmeans for applying the force to the gyroscope to cause precession of the gyroscope in the direction of movement of thegun and at a Tate proportional tothe force, means for developing a force proportional to the rate of change of displacement of the sight and the gyroscope relative to the gun, and means for modifying the effect of the first mentioned force on thel gyroscope by an amount proportional to the last mentioned force during changes of displacement of the sight and gyroscope relative to the gun.

' JAMES D. TEAR.` ELLIO'I'IP. ROSS?V 

